It's difficult to tell whether the insects are the cause of the death of the branch or if they moved in there because the branch had already died. About the only way to know is to collect some of the insects and take them to your local cooperative extension office for identification. They will be able to tell whether they are the culprits, or if they are just opportunists. Contact Extension Svc , Gainesville Hwy, Blairsville, GA 30512 Phone: (706) 745-6197. Good luck with your persimmon tree.